From 5a860740af315f8ab415b785205d3efad5429b21 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Sat, 23 Nov 2013 16:54:01 +0100
Subject: coordinates corrections

---
 raytracer.hs | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/raytracer.hs b/raytracer.hs
index 80fa348..15ebc18 100644
--- a/raytracer.hs
+++ b/raytracer.hs
@@ -13,24 +13,25 @@ type Sphere = (Coord, Double)
 
 degrees = pi / 180
 
-eye = (100, 100, 2)
+eye = (0, 0, 2)
 
 x_of (x, _, _) = x
 y_of (_, y, _) = y
 z_of (_, _, z) = z
 
-sphere1 = ((10, 85, 0), 4)
-sphere2 = ((-10, 45, 0), 4)
+sphere1 = ((40, 85, 0), 4)
+sphere2 = ((40, 45, 0), 4)
 
-alpha1 = 80 * degrees
-alpha2 = -40 * degrees
 
-beta1 = 25 * degrees
+alpha1 = 180 * degrees
+alpha2 = 0 * degrees
+
+beta1 = 20 * degrees
 beta2 = -20 * degrees
 
 floorscale = 1
 
-w = 800
+w = 600
 h = 400
 
 oversampling = 1 -- each pixel is 2x2 rays
@@ -66,11 +67,19 @@ discr source (alpha, beta) (centre, radius) = 4*(( aa * u + bb * v + cc * w )^2
             bb = sin alpha
             cc = sin beta
 
-intersect_sphere :: Coord -> ScreenCoord -> Sphere -> Bool
+intersect_sphere :: Coord -> ScreenCoord -> Sphere -> Double
 intersect_sphere source (alpha, beta) (centre, radius)
-        | discr source (alpha, beta) (centre, radius) > 0 = True
-        | otherwise = False
-
+        | delta > 0 = min ((-b - sqrt(delta)) / (2*a)) ((-b + sqrt(delta)) / (2*a))
+        | otherwise = 0
+            where delta = discr source (alpha, beta) (centre, radius)
+                  a = aa^2 + bb^2 + cc^2
+                  b = 2 * (aa*u + bb*v + cc*w)
+                  u = (x_of source) - (x_of centre)
+                  v = (y_of source) - (y_of centre)
+                  w = (z_of source) - (z_of centre)
+                  aa = cos alpha + cos beta
+                  bb = sin alpha
+                  cc = sin beta
 
 
 
@@ -84,7 +93,7 @@ intersect_floor source (alpha, beta)
 
 floorcolor :: Coord -> ScreenCoord -> Color
 floorcolor source (alpha, beta)
-        | x > 0.5 && x < 0.5 = (0, attn, attn)
+        | x > (-0.5) && x < 0.5 = (0, attn, attn)
         | y > (-0.5) && y < 0.5 = (attn, attn, 0)
         | (round (x/floorscale) `mod` 2) == (round (y/floorscale) `mod` 2) = (attn, 0, 0)
         | otherwise              = (attn, attn, attn)
@@ -99,8 +108,8 @@ skycolor source (alpha, beta) = (60,
 
 pixel_color :: Coord -> ScreenCoord -> Color
 pixel_color source (alpha, beta)
-        | intersect_sphere source (alpha, beta) sphere1 = (200, 0, 0)
-        | intersect_sphere source (alpha, beta) sphere2 = (0, 200, 0)
+        | intersect_sphere source (alpha, beta) sphere1 > 0 = (200, 0, 0)
+        | intersect_sphere source (alpha, beta) sphere2 > 0 = (0, 200, 0)
         | beta > 0  = skycolor source (alpha, beta)
         | beta == 0 = (0, 255, 0)
         | otherwise = floorcolor source (alpha, beta)
-- 
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